Dual wire paper forming apparatus and suction box therefor



3,438,854 OX QEREFOR J. A. MEANS April 15, 1969 DUAL WIRE PAPER FORMING APPARATUS AND SUCTION B Sheet Filed Oct. 29, 1964 ME; 235m Nw Qw kw N \WQ 7 @Q v\\ \m\ GE 7 W 0&9: mam .jom

mwxom 2958 .HH nu l IfiWO 8 i l'llll 4 0 0 0 1 0 4 0 0 mwnzmow mob INVENTOR. JOHN A. MEANS 4 5,, 64M J W his ATTORNEYS.

April 15, 1969 J. A. MEANS 3,438,854

DUAL WIRE PAPER FORMING APPARATUS AND SUCTION BOX THEREFOR Filed Oct. 29, 1964 Sheet 2 of '7 INVENTOR.

JOHN A. MEANS BY f7lmaafiw K his ATTORNEYS.

J. A. MEANS A ril 15, 1969 DUAL WIRE PAPER FORMING APPARATUS AND SUCTION BOX THEREFOR Sheet Filed Oct. 29, 1954 m at INVENTOR.

JOHN A. MEANS his ATTORNEYS.

April 15,1969 MEANS 3,438,854

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his ATTORNEYS.

April 15, 1969 J. A. MEANS 3,438,854

DUAL WIRE PAPER FORMING APPARATUS AND SUCTION BOX THEREFOR Filed Oct. 29, 1964 Sheet 5 of 7 w M g-" FIG. 7

INVENTOR. JOHN A. MEANS 's ATTORNEYS.

Jv A. MEANS A ril 15, 1969 DUAL WIRE PAPER FORMING APPARATUS AND SUCTION BOX THEREFOR Sheet Of7 Filed Oct. 29, 1964 INVENTOR.

JOHN A. MEANS his ATTORNEYS.

SUCTION BOX THEREFOR April 15, 1969 APPARATUS AND DUAL NZRE. PAPER FORMING Sheet Filed Oct. 29, 1954 y fi? INVENTOR. JOHN A. MEANS his ATTORNEYS.

United States Patent US. Cl. 162303 2 Claims ABSTRACT OF THE DISCLOSURE A twin-wire paper-making machine is provided with a forming box having a permeable, stationary, curved forming surface. The box is formed with a plurality of blade means which, while themselves straight in a preferred embodiment, assist in the definition of the curved surface. The orientation of the box and, adjacent thereto, the forming wires, is such that the force of gravity tends in the absence of countervailing forces to effect removal of water through one of the wires more than through the other. One web-contacting wire of the machine is wrapped about a break roll downstream of the curved forming box through an arc of about 6 to facilitate separation of a paper web formed on the machine from the other of the web-contacting wires.

This invention relates to paper-making methods and apparatus and, in particular, to novel and highly-effective methods and apparatus permitting the rapid and economical production of high-quality paper (the term paper is used herein not merely in a specific sense but also in a generic sense to include paperboard and similar products).

The recently-developed twin-wire paper-making machine-Le, a machine in which the paper web is formed between two forming wires-is generally superior to the earlier-developed machines in which the paper web is formed on one forming wire rather than between two. Conventional twin-wire paper-making machines have certain drawbacks, however.

A representative problem encountered with such machines is that they provide insufficient control over the rate of convergence of the twin wires with respect to each other and fail to mount the wires with sufiicient resilience to pass lumps in the stock, snags in the wires, etc. As a result, the formed paper has numerous imperfections and the wires are subject to frequent breakage.

Another problem encountered with twin-wire papermaking machines is that the web tends to separate into two layers where the twin wires are separated from each other by a turning roll about which one of the wires is directed.

Still another problem, which is encountered not only with twin-wire machines but also with the earlier-developed machines referred to above, is that the suction box tops employed therein are expensive and ill-suited to the removal of water from the paper stock.

An object of the present invention is to remedy the problems outlined above.

More particularly, an object of the invention is to provide a novel forming box specifically adapted for use in twin-wire machines.

Another object of the invention is to provide inexpensive suction box tops adapted to facilitate removal of water from an inchoate paper Web highly effectively.

Another object of the invention is to facilitate the use of a twin-wire machine without the attendant danger of web separation at the point where the twin wires are separated from each other.

For the attainment of these and other objects of the invention, a paper-making machine wherein first and sec ond paper-forming foraminous elements such as conventional Fourdrinier wires move in substantially parallel paths at substantially the same velocity in contact with and on opposite sides of an inchoate paper web through at least a part of a forming zone and then separate from each other is provided with means adjacent to the first foraminous element at the locus of separation of the first and second foraminous elements and on the side of the first foraminous element opposite the web for directing the web to follow one of the foraminous elements, the second foraminous element being free of restraining means at the locus of separation of the first and second foraminous elements, whereby the paper web separates from the other of the foraminous elements integrally and without being crushed.

A forming box having a stationary, open, and speciallycurved moving-foraminous-element-contacting surface is also provided. The forming box is herein called a curved forming box, because of the curvature of its moving-foraminous-element-contacting surface. Partition means in the curved forming box divides the box into a plurality of compartments, and vacuum means associated with each compartment establishes an individuallyadjustable vacuum therein.

In certain respects, the invention is an improvement of the invention disclosed in a co-pending application of David E. Robinson for Paper-Forming Apparatus and Methods, Ser. No. 311,278, filed Sept. 16, 1963, noW Pat. No. 3,232,825.

For an understanding of further aspects of the invention, reference is made to the following detailed description of several representative embodiments thereof, in conjunction with the accompanying figures in the drawings, in which:

FIG. 1 is a side elevational schematic view of apparatus constructed in accordance with the invention;

FIG. 2 is a top plan view of one embodiment of a curved forming box constructed in accordance with the invention;

FIG. 3 is a view taken substantially along the line 3-3 of FIG. 2 and looking in the direction of the arrows;

FIG. 4 is a view taken substantially along the line 4-4 of FIG. 2 and looking in the direction of the arrows;

FIG. 5 is a view taken substantially along the line 5-5 of FIG. 2 and looking in the direction of the arrows;

FIG. 6 is a plan view of another embodiment of a curved forming box constructed in accordance with the invention;

FIG. 7 is a view taken substantially along the line 77 of FIG. 6 and looking in the direction of the arrows;

FIG. 8 is a View taken substantially along the line 88 of FIG. 6 and looking in the direction of the arrows;

FIG. 9 is a plan view of another embodiment of a curved forming box constructed in accordance with the invention;

FIG. 10 is a view taken substantially on the line 10-10 of FIG. 9 and looking in the direction of the arrows; and

FIG. 11 is a view taken substantially along the line 11-11 of FIG. 9 and looking in the direction of the arrows.

FIG. 1 shows a wide fiat stream of paper stock 19 ejected at high speed from a slice 20, the wide dimension of the stream extending into the plane of the figure. The stock 19 is directed between lower and upper breast rolls 22, 24 rotatably mounted in spaced-apart relation with respect to each other. The rolls 22, 24 may be solid or open but are preferably solid for greater rigidity. Similarly, the spacing with respect to each other of the points of their respective circumferences closest to each other may be varied but is preferably greater than the thickness in the plane of FIG. 1 of the jet of stock 19 to avoid pumping of the stock. A lower movable paperforming foraminous element 26 such as a conventional bronze Fourdrinier wire is trained about the lower breast roll 22, and an upper movable paper-forming foraminous element 28 such as a conventional bronze Fourdrinier wire is trained about the upper breast roll 24. A movable foraminous drainage element 30, which may be made of a tough plastic such as nylon, is preferably also trained about the lower breast roll 22, between it and the lower forming wire 26.

A stationary forming box 32 constructed in accordance with the invention and referred to herein as a curved forming box is mounted beneath the foraminous drainage element 30 in closely-spaced-apart relation to the lower breast roll 22. The elements 26, 28, 30'are trained about the open, curved surface 33 of the forming box 32 in such a way that the forming box 32 assists in the establishment of a convergence between the movable paperforming foraminous element 26 and the movable foraminous drainage element 30 on the one hand and the paperforming foraminous element 28 on the other. As noted above, the surface 33 of the forming box 32 adapted to contact the movable foraminous drainage element 30 (or, if the element 30 is not employed, the movable paperforming foraminous element 26) is curved. In a cross section taken in the plane of FIG. 1, the curve described by the surface 33 may be part of a circle, parabola, hyperbola, or sine wave, or it may be a French curve or some other curve. In a typical case, the curve is part of a circle, which means that the surface 33 itself describes part of a cylinder. The surface 33 preferably curves through an arc of about as disclosed in the co-pending Robinson application Ser. No. 311,278 referred to above.

The curvature of the movable-forarninous-element-contacting surface 33 facilitates the subjection of the inchoate web therebetween to a progressively increasing pressure as the web traverses the surface. The curvature of the surface 33 is related, moreover, to the rate of convergence of the paper-forming foraminous elements 26, 28 and to the tension to which the upper element 28 must be subjected in order to perform its intended function. In general, the smaller the radius of curvature of an arc of a given number of degrees (or, for curves other than cylindrical ones, the sharper the curvature), the more abrupt the convergence of the paper-forming foraminous elements 26, 28 and the less the tension to which the upper element 28 must be subjected in order to maintain the desired relation between it and the element 26 and, more particularly, in order to maintain the desired pressure (force per unit area) on the inchoate web.

Thus, a radius of curvature that is quite large or a curve that is not sufficiently sharp is not optimum; it requires great tension on the element 28 in order to prevent unacceptable bulging thereof from the element 26. Such tension tends to wrinkle and even rupture the element 28 and, in any event, to shorten its life. Similarly, a radius of curvature that is quite small or a curve that is quite sharp is also not optimum; it results in a rate of convergence of the elements 26, 28 that exceeds that facilitating production of the highest-quality paper.

In accordance with a preferred embodiment of the invention, the surface 33 is curved cylindrically through an arc of 20, as noted above, and about a five-foot radius. That is, the surface 33 is a portion of an imaginery cylinder having a diameter of ten feet. It has been found that the resulting curvature is an optimum one for the production of paper at speeds within the range of about 1500 to 2500 feet per minute, both from the'standpoint of facilitating the proper rate of convergence between the paper-forming foraminous elements 26 and 28 and from the standpoint of prolonging the life of the element 28.

In accordance with the present invention, moreover, the curved forming box 32 is tilted counterclockwise with .4 respect to the orientation disclosed in the aforesaid Robinson application through an angle of approximately 3, so that, at the upstream end 34 of the curved forming box 32, the inclination of the curved surface 33 and hence of the paper-forming foraminous element 26 and foraminous drainage element 30 is approximately 23 above the horizontal in the direction of web movement. Similarly, at the downstream end 36 of the curved surface 33, the inclination of the surface 33 and hence of the elements 26, 28, and 30 is approximately 3 above the horizontal in the direction of web movement. The reason for this orientation of the curved forming box 32 is that, in a maner set forth below, it facilitates the provision of a humped construction of the portion of the forming zone downstream of the curved forming box 32 and hence the separation of the element 28 from the paper web and the elements 26 and 30 without crushing of the web or separation of the web into a plurality of layers.

Suction boxes 38, 40, 42, and 44 and atop scraper 46, all of which may be conventional per se, are provided for dewatering the inchoate web at opposite sides thereof. In accordance with the present invention, however, the suction boxes 38, 40, 4'2, and 44 are spaced apart from each other and arranged with their tops sloping in the direction of Web movement at an angle of approximately 3 above the horizontal. Similarly, the paper-forming-forarninouselement-contacting surface of the scraper blade 48 for the top scraper 46 slopes upwardly in the direction of web movement at an angle of about 3.

Downstream of the suction box 44, training means such as a vacuum break roll 50 rotatable about its axis and having a suction box 52 is provided in accordance with the invention. The suction box 52 of the vacuum roll 50 is urged against the element 30 (or, if the element 30 is not employed, against the paper-forming forminous element 26) so that the elements 26, 28, 30 move in substantially a straight line from the downstream end 36 of the curved forming box 32 to the suction box 52 upwardly in the direction of web movement at an angle of about 3. The element 28 continues to move substantially in the same straight line to a tail roll 54, about which it is trained, and loops back to the upper breast roll 24. The roll 54 is mounted above and somewhat downstream of the roll 50.

Downstream of the roll 50, additional suction boxes 56, 58, 60, 62 are provided. The suction boxes 56, 58, 60', 62 may be conventional per se, but they are spaced apart from each other and their upper surfaces are inclined downwardly 3 in the direction of web movement so that, in its run from the roll 50 to a roll 72 downstream thereof, the element 26 lies in a plane inclined about 3 downwardly in the direction of web movement. Thus, the angle formed by the portions of the elements 26, 28, 30' immediately upstream of the roll 50 and the portions of the elements 26, 30 immediately downstream of the roll 50 is about 6, and the web executes a turn of about 6 as it passes the roll 50.

At the locus of contact of the vacuum roll 50 with the wire 30, therefore, the element 28 is separated from the elements 26, 30. The suction box 52 applies suction to the web and assures that the web continues to travel with the elements 26, 30 rather than with the element 28. It is to be noted that the element 28 is free of restraining means (such as a roll) opposite the suction box 52 where the elements 26, 30 and the web on the one hand separate from the element 28 on the other.

This arrangement permits separation of the elements 26, 30 and the web on the one hand from the element 28 on the other without separation of the web and without crushing the web.

If the roll 50 does not form a hump in the forming zone-if, in other words, the elements 26, 28, 30 extend in a straight line from the downstream end 36 of the curved forming box 32 to the point where the element 28 separates from the web and the elements 26, 30, and the elements 26, 30 extend in a continuation of the same straight line downstream of the locus of separation of the element 28 from the elements 26, 30 and the webthe roll 54 is in virtual contact with one face of the web. That face of the web, being wet, tends to follow the surface of the roll 54, even if the surface is open. This causes separation of the web, which at this point in its formation is not very cohesive.

Similarly, if the rolls 50 and 54 are mounted in opposed nip-defining relation, so that the vacuum box 52 in the roll 50 is positioned to maintain the web on the element 26, the arrangement is unsatisfactory; in such case, the nip formed by the rolls 50 and 54 tends to crush the web, which at this point in its manufacture is not sufficiently set to withstand strong pressures.

Nor is it satisfactory to mount the roll 54 opposite the roll 50 but spaced apart therefrom, for in such case the element 28 downstream of the curved forming box 32 is not flush against the web but diverges therefrom in the direction of web motion. This is particularly true because, as noted above, a certain amount of tension must be maintained on the element 28 in order to maintain the desired relation between it and the element 26 in the vicinity of the curved forming surface 33 of the forming box 32. The separation of the paper-forming foraminous element 28 from the web downstream of the downstream end 36 of the curved forming box 32 results in a sacrifice of many of the advantages of twin-wire formation.

Thus, of the above-disclosed possible alternative structures, only the arrangement in accordance with the present invention provides satisfactorily for the separation of the paper-forming foraminous elements of a twinwire machine without crushing or separating the inchoate web.

Between the suction boxes 56 and 58, the element 30 is trained over a roll 64 rotatable about its axis and having its upper circumference tangent to the plane of travel of the elements 26 and 30 in the forming zone downstream of the roll 50. The element 30 is then trained around a roll 66, a roll 68, and a roll 70, each of the three rolls being rotatable about its respective axis. The element 26 is passed over the section boxes 58, 60, 62 with the web and trained about a rotatable roll 72 and then about the same roll 68 as the element 30. The ele meat 26 bypasses the roll 70, however, and returns via appropriate tension rolls (not shown) to the roll 22, where it rejoins the element 30.

FIGS. 25 show in detail one form of curved forming box constructed in accordance with the invention.

FIG. 2 shows a first plurality of blades 74 disposed on the right half of the box as seen in the figure, and a second plurality of blades 76 disposed on the left half of the box. The blades 74 and 76 may be about of an inch or less thick in a transverse direction parallel to the plane of stock flow and substantially transverse of the longitudinal direction or direction of stock flow. The latter direction is indicated by the arrow at the bottom of the figure.

The blades 74 are disposed in uniformly-spaced-apart (by, say, A of an inch) planes parallel to one another and normal to the portions of the elements 26, 28, 30 transversing the curved forming box 32. Similarly, the blades 76 are disposed in uniformly-spaced-apart planes parallel to one another and normal to the portions of the elements 26, 28, 30 transversing the curved forming box 32. Further, in order to prevent shadow marking of the web, the blades 74 should be angled to give to one part of the water passing therebetween a first component of motion normal to the direction of movement of the web, and the blades 76 should be angled to give to another part of the water passing therebetween a second component of motion opposite to the first component of motion.

To this end, the blades 74 on the one hand and 76 on the other are given oposite inclinations with respect to the machine direction or direction of travel of the inchoate paper web over the curved forming box. This construction is effective to divert the water expressed from the web and between the blades 74 on the one hand and 76 on the other in opposite direction so as not to produce a net reaction on the wire. The wire thus is not urged towards either side of the machine but runs true. The inclination of the blades also produces a slight scraping effect which facilitates the removal of water.

Transverse support members 78 (FIG. 3) are provided for the purpose of bracing the "blades 74 and 76 and permitting them to withstand the considerable stress to which they are subjected when a vacuum is applied within the curved forming box.

As FIG. 4 shows, the curved forming box is preferably divided into a plurality of suction-box compartments 80, 82, 84, 86, 88 disposed in a row extending longitudinally of the direction of the web movementi.e., the direction indicated by the arrow at the top of the figure. The number of suction box compartments should be at least three and is preferably five. Each suction box is provided with a separate white-water drain 90, 92, 94, 96, 98, as shown in FIGS. 2, 4, and 5. (It is to be noted ,that FIGS. 4 and 5 are views from opposite directions, so that the direction of web movement is from left to right in one figure and from right to left in the other.) The drains 90, 92, 94, 96, 98 are either sized in accordance with the amount of water to be removed thereby or provided with valves to control their water-draining capacity. In this way, a water seal is maintained across the cross section of each drain. The drains are displaced laterally from the forming area of the curved forming box, as shown in FIG. 2.

Each suction box 80, 82, 84, 86, 88 is provided also with a separate air suction line 100, 102, 104, 106, 108. The suction lines may be connected to a common manifold (not shown) and may be provided with individually-adjustable valve means (not shown) whereby individually-adjustable vacuums in the suction boxes 80, 82, 84, 86, 88 may be provided. The vacuum in the suction boxes 80, 82, 84, 86, 88 increases progressively in the direction of web movement, the box having the lowest vacuum (greatest absolute pressure) and the box 88 having the highest vacuum (least absolute pressure). The suction box 88 may have a vacuum ranging up to about 12 inches of water.

The suction boxes 80, 82, 84, 86, 88 are separated from each other by partitions, a first partition separating the first two boxes 80, 82, a second partition 112 separation the second and third boxes 82, 84, a third partition 114 separating the third and fourth boxes 84, 86 and a fourth partition 116 separating the fourth and fifth boxes 86, 88.

Each partition 110, 112, 114, 116 is connected to one of a plurality of sloping partition blades 118, 120, 122, 124. Each blade 118, 120, 122, 124 extends from one slde of the forming box to the other transversely of the direction of web movement and from the upper edge of the corresponding partition 110, 112, 114, 116 to the locus of contact of the element 30 with the curved forming box. In this way, the divisions of the suction boxes 80, 82, 84, 86, 88 of the curved forming box are maintained all the way to the element 30 shown in FIG. 1 so that individually-adjustable vacuums can be maintained in the boxes 80, 82, 84, 86, and 88 by the vacuum-producing means.

The intermediate sloping supports 126 need not run all the way to the locus of the element 30 and preferably terminate short thereof. The partition blades 118, 120', 122, 124 and the intermediate sloping supports 126 are inclined at about 45 to the horizontal, diverging downwardly from the web in the direction of web movement, to facilitate removal of water.

FIGS. 68 show another embodiment of a curved forming box constructed in accordance with the invention. In this embodiment, the box has a number of transverse blades 130, 132, etc., described below, but is devoid of longitudinal foraminous-element-contacting bladesi.e., devoid of blades which extend in the direction of web movement and which are adapted to contact the element 30. As a result, the elements 26, 28, 30 and the web tend to follow paths composed of a large number of straight segments, each segment being limited by the supporting surfaces 128 of the adjacent blades 130, etc., and being very small. The change in direction of adjacent segments is slightapproximately 1, for example, where the blades are approximately in number and the total are of the curved surface of the forming box is about 20.

An advantage of this construction is that the element can be eliminated and a bronze wire run directly on the curved forming box without undue wear of the bronze wire, because there is no lattice. A further advantage of the construction is that the forming box is readily and economically manufactured. In particular, although the advantages of the curved forming box are realized, it is not necessary to machine a curve.

The sloping partition blades 132, 134, 136, 138 are continuations of the partition members 140, 142, 144, 146 and facilitate the division of the box into a plurality of compartments, in this case five, each of which may be provided with a different degree of vacuum as disclosed above. Short sloping blades 130 extend from the locus of the element 30 downwardly to a point somewhat less than half way to the plane of the upper edges of the partitions 140, 142, 144, 146. A longitudinally-extending web 148 may be provided for the purpose of supporting the sloping blades 130, 132, 134, 136, and 138.

FIGS. 9-11 show another embodiment of curved forming box constructed in accordance with the invention. FIG. 9 shows two groups of perforations 148 and 150. The perforations 148 to the right of the machine center line are canted to the right in the direction of web movement, while the perforations 150 to the left of the machinecenter line are canted to the left. The perforations 148 and 150 are about A of an inch wide. Between the perforations, lands 152 and 154, respectively, also about A of an inch wide, are provided. The perforations are, moreover, arranged in a plurality of rows 156, 158, 160, 162, and 164 separated by lands 166, 168, 170, and 172. The groups of perforations 148, 150 are thus subdivided into a number of smaller groups. Each land 166, 168, 170, and 172 is about A of an inch wide in the direction of web movement. Preferably, the suction-box top is molded, and the lands are covered with silicon carbide, which is polished to a mirror-like finish. The suction-box top is thus longwearing and easy to manufacture. Moreover, its low friction increases wire life.

Thus, there is provided in accordance with the invention novel and highly-effective papermaking methods and apparatus enhancing the worth of the twin-wire machine and eliminating its chief drawbacks. In particular, it will be observed that, in the entire length of the forming zone (FIG. 1), there is no point where restraining means such as rolls, scrapers, and suction boxes are mounted in opposed relation against the movable foraminous elements on opposite sides of the web. Thus, lumps in the stock, snags in the movable foraminous elements, etc., can pass without disrupting the web, breaking the foraminous elements, or otherwise doing serious harm. Machine down time and hence the cost of paper manufacture are substantially reduced by the methods and apparatus of the invention.

Many modifications of the specific embodiments disclosed herein will readily occur to those skilled in the art. For example, while the schematic view of FIG. 1 shows a machine that is substantially horizontal, the forming zone immediately before and after the roll sloping upwardly at an angle of about 3 and downwardly at an angle of about 3, respectively, the present invention of means for separating the elements 26 and 28 without separating or crushing the web is also operative in machines having other orientations. Further, while the suction box 52 in the roll 50 has been disclosed as exerting a suction on the web to retain it on the element 26, it may also apply air pressure to the web to direct it to follow the element 28. This may be done on a machine which is patterned, for example, after the machine of FIG. 1 imaged through a plane mirror lying in a horizontal plane above or below the machine of FIG. 1 and which is further modified as compared to the machine of FIG. 1 in having the roll 54 mounted considerably downstream of its position in FIG. 1, in having the elements 26, 30 trained about the roll 50 and then directly back to the roll 22, and in having the suction boxes 38, 40, 42, 44 and 56, 58, 60, 62 mounted adjacent to the element 28 rather than 30. Accordingly, the invention is to be construed as including all of the modifications thereof which fall within the scope of the appended claims.

I claim:

1. A paper-making wet-end machine comprising the combination of first and second foraminous elements movable in substantially parallel paths at substantially the same velocity in contact with and on opposite sides of an inchoate paper web through at least a part of a forming zone and training means adjacent to said first foraminous element for training said first foraminous element through an arc of about 6 and separating said first foraminous element from said second foraminous element, said first foraminous element approaching said training means at an angle 3 above the horizontal and departing from said training means at an angle 3 below the horizontal and said second foraminous element being free of restraining means at the locus of separation of said first and second foraminous elements, whereby said paper web is separable from one of said foraminous elements integrally and Without being crushed.

2. In a forming box for mounting on a paper-making machine to facilitate the making of paper, said box having a surface operatively associated with a foraminous paper-forming element moving in a given direction, the improvement comprising the combination of (a) a plurality of blade means having edges extending transversely of said direction of movement and assisting in the definition of said surface, said surface being (i) permeable,

(ii) stationary, and

(iii) curved in said direction of movement;

(b) partition means dividing said box into a plurality of compartments; and

(c) individually adjustable vacuum means for establishing individually-adjustable vacuums in said compartments.

References Cited UNITED STATES PATENTS 3,215,594 11/1965 Baxter et a1 162-303 3,224,928 12/ 1965 Lee et a1 162-203 X 3,232,825 2/ 1966 Robinson 162-4303 X 3,262,841 7/1966 Embry 162-203 X 3,311,533 3/1967 Montigny et al. 162-303 X FOREIGN PATENTS 279,570 10/ 1914 Germany.

S. LEON BASHORE, Primary Examiner.

US. Cl. X.R. 

